No description available.

With the advent of cephalometrics in the 1930s, numerous studies have focused on the profile of a face to achieve a more esthetic orthodontic treatment outcome. With such heavy emphasis on facial esthetics, a shift in focus from the profile view to the oblique view has become necessary as the smile in the oblique view is what the general public evaluates. The purpose of this pilot study was to determine whether the current tools for diagnosis and treatment evaluation are sufficient. Currently, 2-dimensional composite photographs are utilized in evaluating the soft tissue. At Temple University, 3-dimensional images, which show all sides of the patient's face, are used adjunctively to 2-dimensional composite photographs. In this study, faculty members at the Temple University Department of Orthodontics were asked to complete surveys after viewing two different image modalities, 2-dimensional images and a 3-dimensional video of the same patient. They were asked to fill out the soft tissue goals for specific facial landmarks. Patient photos were in the smiling view as current literature lacks studies on this view. Faculty members' responses from analyzing the 2-dimensional images and 3-dimensional video for each patient were compared to determine which areas had frequent discrepancies from using two different image modalities. During the survey, a voice recorder captured any comments regarding the images. The ultimate goal of this qualitative pilot study was to identify when 3-dimensional imaging is necessary in treatment planning and evaluation, with an added hope to further advance research in 3-dimensional imaging and its vast possibilities to advance the field of orthodontics. Based on the data collected, the following conclusions were made: 1. The qualitative data highlighted that 3-dimensional imaging would be necessary in cases with skeletal deformities. 2. In the oblique view, 3-dimensional imaging is superior than 2-dimensional imaging by showing more accurate shadow, contour, and depth of the soft tissue. 3. Further improvement is necessary to create a virtual patient with treatment simulation abilities. 4. The comfort level among orthodontists of 2-dimensional imaging was higher than 3-dimensional imaging. With more widespread use of 3-dimensional imaging, more orthodontists may gradually reach a higher comfort level in using this relatively new technology. 5. Faculty members expressed high willingness to use 3-dimensional imaging if improvement in new technology could allow for more manipulation and accurate soft tissue prediction. 6. 3-dimensional imaging is superior in its efficiency, quick capture time, and lack of need for multiple images. Implementation of 3-dimensional imaging could streamline the records process and help with practice efficiency without compromising the image quality. 7. Both patients and orthodontists may benefit from using 3-dimensional imaging. Patients can see an accurate representation of themselves and possibly view their own treatment simulation upon further improvement in current technology. Orthodontists would benefit with much more accurate images that may serve as the virtual patient. 8. Besides the exorbitantly high cost, faculty members thought that more advances were needed and the current benefit was not great enough to justify the investment. The results were consistent with other studies that used the oblique view in that the 2-dimensional oblique view lacks depth and does not provide adequate information. With further improvement in current 3-dimensional imaging, this technology can benefit orthodontists in visualizing their patients. In addition, patients can benefit by hopefully seeing a live and accurate simulation of themselves instantly as a virtual patient. With these benefits of 3-dimensional imaging, it may one day be the new standard in patient records in the field of orthodontics. / Oral Biology

Studies have shown that modeling errors due to unaccounted for soft-tissue deformations – known as soft-tissue artifact (STA) – can reduce the efficacy and usefulness of musculoskeletal simulations. Recent work has proven that adding degrees of freedom (DOF) to the joint definitions of a musculoskeletal model’s lower limbs can significantly change the prediction of an individual’s kinematics and dynamics while simultaneously improving estimates of their mechanical work. This indicates that additional modeling complexity may mitigate the effects of STA. However, it remains to be determined whether adding DOF to the lower limb joints can impact a model’s satisfaction of Newton’s Second Law of Motion, or whether a specific number of DOF must be incorporated in order to produce the most biomechanically accurate simulations. To investigate these unknowns, I recruited ten subjects of variable body-mass-indices (BMI) and recorded subject walking data at three speeds normalized by Froude number (Fr) using optical motion capture and an instrumented treadmill (eight male, two females; mean ± s.d.; age 21.6 ± 2.87 years; BMI 25.1 ± 5.1). Then, I added DOF to the lower limb joints of OpenSim’s 23 DOF lower body and torso model until it minimized the magnitude of the pelvis residual forces and moments for a single, representative subject trial (BMI = 24.0, Fr = 0.15). These artificial residual forces and moments are applied at the pelvis to maintain the model’s orientation in space by satisfying Newton’s Second Law. Finally, I simulated all 30 trials with both the original and the edited model and observed how the biomechanical predictions of the two models differed over the range of subject BMIs and walking speeds. After applying both the original and the edited model to the entire data set, I found that the edited model resulted in statistically lower (α = 0.05) residual forces and moments in four of the six directions. Then, after investigating the impact of changes in BMI and Froude number on these residual reductions, I found that two of the six directions exhibited statistically significant correlations with Froude number while none of the six possessed correlations with BMI. Therefore, adding DOF to the lower limb joints can improve a model’s dynamic consistency and combat the effects of STA, and simulations of higher speed behaviors may benefit more from additional DOF. For BMI, it remains to be determined if a higher BMI indicates greater potential for residual reduction, but it was shown that this method of tuning the model for one representative subject was agnostic to BMI. Overall, the method of tuning the model for one representative subject was found to be quite limited. There were multiple subject trials for which reduced residuals corresponded to drastic changes in kinematic and dynamic estimates until they were no longer representative of normal human walking. Therefore, it is possible to improve dynamic consistency by adding DOF to the lower limb joints. But, for biomechanically relevant estimates to be consistently preserved and soft-tissue artifact to be completely minimized, subject-specific model tuning is likely necessary. / Mechanical Engineering

Injury of the manus is an important cause of morbidity and function loss in dogs, especially working breeds. These injuries may cause foreign body retention and can lead to persistent infection. Accurate methods for diagnosis and localization of pathology in this anatomically complex region are critical to minimize patient morbidity, guide surgical planning, and improve case outcomes. The anatomy of the canine manus was evaluated with computed tomography (CT), magnetic resonance imaging (MRI), and transverse anatomic sections. Most structures identified on transverse sections were visible on both CT and MRI images. Detail in the osseous structures was better in CT images, while MRI provided increased contrast of soft-tissue structures. To test the hypothesis that diagnostic accuracies of CT, MRI, and ultrasound differ for detection of acute wooden foreign bodies in the canine manus, we inserted wooden splinters into canine cadaver manus and imaged each manus with all three modalities. Receiver operating characteristic curve analysis demonstrated that CT was most accurate for detection of acute wooden foreign bodies, followed in turn by ultrasound and MRI. Diseases in the human hand and foot are often confined by soft-tissue spaces, but similar structures have not been described in the dog. To determine if these spaces are present in the canine manus, we injected contrast medium into likely spaces and compartments in cadaver specimens, imaged the limbs with CT, and dissected the injected manus specimens. We found thirteen discrete soft-tissue spaces and five myofascial compartments that are similar to those described in the human hand. To test the hypothesis that spread of disease in the canine manus can be modeled and predicted, we injected cadaver interdigital web spaces with contrast medium, imaged them with CT, and dissected them. We found that the pattern of contrast agent spread, as a model of infection, was predictable and unique to the initial injection site. Findings from these cadaver studies improve our understanding of anatomy, imaging of wooden foreign bodies, and likely patterns of disease extension in the canine manus. Future studies are needed to test the utility of this information for surgical planning in affected clinical patients. / Ph. D.

Histotripsy is a non-thermal, non-invasive focused ultrasound therapy using controlled acoustic cavitation to mechanically disintegrate tissue into an acellular homogenate. Histotripsy applies microsecond-length, high pressure (> 10 MPa) pulses to initiate the rapid expansion and collapse of nuclei in a millimeter-scale focal region, applying large stresses and strains to targeted tissues. The cavitation "bubble cloud" generated during histotripsy treatment can be visualized in real time on ultrasound imaging, assisting with treatment guidance and monitoring. Past studies have demonstrated histotripsy's potential for a variety of applications, but histotripsy has not yet been investigated for superficial musculoskeletal tumor ablation. Additionally, preliminary investigations using histotripsy to ablate brain tumors are underway, but require advanced histotripsy devices capable of overcoming attenuation of the therapeutic ultrasound signal by the skull and rely on MRI for real-time guidance. As a result, open questions remain regarding ultrasound-guided histotripsy for brain tumors. Early evidence also suggests that histotripsy ablation may induce immunogenic changes in the tumor microenvironment. Continued research is needed to explain and corroborate these findings under conditions more immunologically representative of human cancers, such as in large animal models with spontaneous tumors. This dissertation investigates the safety and feasibility of using ultrasound-guided histotripsy to ablate superficial soft tissue sarcomas (STS), osteosarcomas (OS), and brain tumors and considers the immunological impacts of histotripsy treatment for STS and OS. The research described herein (1) investigates the ability of histotripsy to treat superficial STS tumors in companion animals with spontaneous tumors, (2) investigates the feasibility of treating bone tumors with histotripsy through a series of ex vivo and in vivo studies, and (3) applies histotripsy for the minimally invasive treatment of superficial brain tumors. The completion of this dissertation will provide significant insight into the ability of ultrasound-guided histotripsy to treat novel tumor types (i.e., STS, OS, and brain tumors) and the potential role of histotripsy in veterinary medicine. Future work will build upon the studies detailed in this dissertation to optimize ultrasound-guided histotripsy for the treatment of complete STS, OS, and brain tumors in veterinary and human patients. / Doctor of Philosophy / Histotripsy is a non-invasive focused ultrasound therapy that mechanically breaks down targeted tissues through acoustic cavitation. Histotripsy is currently being developed for a number of clinical applications, including tumor ablation, but its potential for treating many cancer types remains unknown. Histotripsy uses very short, high pressure ultrasound pulses to initiate the nucleation of bubbles in the target region. These bubbles then expand and rapidly collapse to impart large stresses and strains on surrounding tissues, leaving behind only acellular debris. The cavitation "bubble cloud" generated during histotripsy treatment can be visualized on ultrasound imaging, offering real-time treatment guidance and monitoring. Histotripsy has not yet been investigated for superficial musculoskeletal tumor ablation, and preliminary studies using histotripsy to ablate brain tumors are underway, but require advanced histotripsy devices still under development. As a result, open questions remain regarding histotripsy ablation as a treatment for musculoskeletal and brain tumors. Additionally, early evidence suggests that histotripsy ablation may be able to stimulate an immune response, treating not only the targeted tumor but also multifocal or metastatic disease. Continued research is needed to explain and corroborate these findings under conditions more similar to human cancers, such as in large animal models with naturally-occurring tumors. This dissertation investigates the safety and feasibility of using ultrasound-guided histotripsy to ablate superficial soft tissue sarcomas (STS), osteosarcomas (OS), and brain tumors and considers the immunological impacts of histotripsy treatment for STS and OS. This research (1) investigates the ability of histotripsy to treat superficial STS tumors in companion animals with spontaneous tumors, (2) investigates the feasibility of treating bone tumors with histotripsy through a series of ex vivo and in vivo studies, and (3) applies histotripsy for the minimally invasive treatment of superficial brain tumors. The completion of this dissertation will provide significant insight into the ability of ultrasound-guided histotripsy to treat novel tumor types (i.e., STS, OS, and brain tumors) and the potential role of histotripsy in veterinary medicine. Future work will build upon the studies detailed in this dissertation to optimize ultrasound-guided histotripsy for the treatment of complete STS, OS, and brain tumors in veterinary and human patients.

The purpose of this dissertation was to study the effects of graft pretension in anterior cruciate ligament (ACL) reconstruction through a series of experiments. First, an in vitro study of 5 human knees was conducted to determine if intact joint kinematics could be restored when using the ideal graft - the intrinsic ACL. The ACL tibial insertion site was freed, and pretensions of 0, 10, 20, 30, and 40 N were applied to the ligament using a custom designed load cell connection. Kinematics during a simulated active extension were compared to those of the intact knee. Intact knee kinematics were not restored. Pretensions that best restored tibial anterior/posterior translation and internal/external rotation ranged from 0-40 N. Furthermore, the pretensions that best restored these kinematic variables were widely disparate in two specimens. Second, the in vitro kinematics during a simulated active extension of human and porcine knees were compared and contrasted both prior to and following transection of the ACL. The ACL limited: (1) tibial anterior translation in both species, (2) tibial internal rotation in humans, and (3) tibial external rotation in pigs. Differences in kinematic patterns for tibial internal/external rotation and abduction/adduction between the species was explained by requirements for biped and quadruped stances. Third, the mechanical characteristics of porcine patellar tendon (PT) were investigated by uniaxial tensile testing at two strain rates. Patella-PT-tibia complexes from freshly sacrificed skeletally immature and mature animals were loaded to failure at elongation rates of 20 and 200 mm/min. Both strain rate and skeletal maturity significantly affected failure mode, tangent modulus, and ultimate stress of the tendons, and hence are important considerations in the mechanical evaluation of porcine PT. Fourth, ACL reconstructions were performed using pretensions of 10 or 20 N in an in vivo porcine model with a specially designed load cell/telemetry system to monitor graft load. Graft pretension was seen to increase during fixation with interference screws. Following sacrifice at 4 weeks, tissues were mechanically, histologically, and biochemically analyzed. A pretension of 20 N resulted in a tissue more similar to the intrinsic ACL. / Ph. D.

Ziel dieser Studie war es, die Wahrnehmung von fazialen und dentalen Asymmetrien bei Kindern und Jugendlichen zu untersuchen und zu ermitteln, wie diese Asymmetrien ihr psychosoziales und emotionales Wohlbefinden beeinflussen.:1 Einführung 1.1 Mundgesundheitsbezogene Lebensqualität 1.2 Dentale Mittellinienverschiebung 1.2.1 Wahrnehmung von Mittellinienverschiebungen 1.3 Dentofaziale Asymmetrien 1.4 Stereofotogrammetrie 2 Ziel der Studie 3 Publikationsmanuskript 4 Zusammenfassung der Arbeit 5 Literaturverzeichnis 6 Anlagen 6.1 Darstellung des eigenen Beitrags 6.2 Selbstständigkeitserklärung 6.3 Tabellarischer Lebenslauf und Publikation 6.4 Danksagung

Yes / Most of surgical simulators employ a linear elastic model to simulate soft tissue material properties due to its computational efficiency and the simplicity. However, soft tissues often have elaborate nonlinearmaterial characteristics. Most prominently, soft tissues are soft and compliant to small strains, but after initial deformations they are very resistant to further deformations even under large forces. Such material characteristic is referred as the nonlinear material incompliant which is computationally expensive and numerically difficult to simulate. This paper presents a constraint-based finite-element algorithm to simulate the nonlinear incompliant tissue materials efficiently for interactive simulation applications such as virtual surgery. Firstly, the proposed algorithm models the material stiffness behavior of soft tissues with a set of 3-D strain limit constraints on deformation strain tensors. By enforcing a large number of geometric constraints to achieve the material stiffness, the algorithm reduces the task of solving stiff equations of motion with a general numerical solver to iteratively resolving a set of constraints with a nonlinear Gauss–Seidel iterative process. Secondly, as a Gauss–Seidel method processes constraints individually, in order to speed up the global convergence of the large constrained system, a multiresolution hierarchy structure is also used to accelerate the computation significantly, making interactive simulations possible at a high level of details . Finally, this paper also presents a simple-to-build data acquisition system to validate simulation results with ex vivo tissue measurements. An interactive virtual reality-based simulation system is also demonstrated.

In this dissertation, the accuracy and reliability of non-linear finite element computations in application to surgical simulation is evaluated. The evaluation is performed through comparison between the experiment and finite element analysis of indentation of soft tissue phantom and human brain phantom. The evaluation is done in terms of the forces acting on the cylindrical Aluminium indenter and deformation of the phantoms due to these forces. The deformation of the phantoms is measured by tracking 3D motions of X-ray opaque markers implanted in the direct neighbourhood under the indenter using a custom-made biplane X-ray image intensifiers (XRII) system. The phantoms are made of Sylgard® 527 gel to simulate the hyperelastic constitutive behaviour of the brain tissue. The phantoms are prepared layer by layer to facilitate the implantation of the X-ray opaque markers. The modelling of soft tissue phantom indentation and human brain phantom indentation is performed using the ABAQUSTM/Standard finite element solver. Realistic geometry model of the human brain phantom obtained from Magnetic Resonance images is used. Specific constitutive properties of the phantom layers determined through uniaxial compression tests are used in the model. The models accurately predict the indentation force-displacement relations and marker displacements in both soft tissue phantom indentation and human brain phantom indentation. Good agreement between the experimental and modelling results verifies the reliability and accuracy of the finite element analysis techniques used in this study and confirms the predictive power of these techniques in application to surgical simulation.

Chronic posterior compartment syndrome (CPCS) of the leg is a pathological condition which is often encountered by participants in exercise related activities such as running. To date no successful conservative treatment approach existed for the condition. The mainstay of the management of the condition at present is the surgical release of the involved fascia that surrounds the compartment. The main aim of the research project was thus to develop a successful conservative treatment approach for the symptoms of CPCS. It was identified that the current theoretical base did not incorporate the continuous and relatively inelastic nature of the fascia which plays an important role in the condition. Based on an extended literature review, muscles which are linked to the posterior compartment via the myofascial tissue were identified. Tightness in these clinically significant muscles is able to induce stresses in the myofascial chain which could ultimately influence stresses in the posterior compartment of the leg. The release of tightness in these muscles external to the posterior compartment through soft tissue mobilization techniques provides an effective conservative treatment approach for the symptoms of CPCS. A revised model for the pathogenesis of CPCS was developed which formed the basis for treatment interventions. The revised theoretical model for the pathogenesis of CPCS was validated based on a mixed-methodological approach which included a series of exploratory as well as explanatory case studies. This qualitative approach was supplemented by quantitative experiments in which the causal relationships of the condition on certain biomechanical aspects were explored. The treatment interventions had a hundred percent success rate and the results of the experimental research conducted also supports the new theoretical model for the pathogenesis of CPCS. / Thesis (DPhil)--University of Pretoria, 2008. / Biokinetics, Sport and Leisure Sciences / unrestricted